When meditation teachers address the pursuit of enlightenment with their students, they either discuss the gradual or sudden approach. The gradual approach focuses on the value of virtue and on the accumulation of wholesome karma. Meditation techniques which concentrate and calm the mind are taught. The cultivation of mindfulness and clear comprehension is encouraged. The mind thus becomes a precise instrument for perceiving things as they really are. In the gradual approach, wisdom is seen as an unfolding process and even enlightenment is seen to progess in stages.

In the sudden approach, however, the teacher's perspective is that we all have Buddha nature and that we cannot "practice" to become what we already are. Concerning oneself with virtue will not lead to the goal since cultivating karma, even wholesome karma, is still involving oneself with the phenomenal world. Even the quest for enlightenment is seen as keeping oneself trapped within a dualistic conceptual framework. When the student makes statements that belie the fact that he or she is already enlightened, the teacher points out the errors in his or her thinking.

Both approaches are valid and students at different stages of development gravitate to one or the other of these schools of thought. Although it is not immediately clear to the casual observer, what both schools have in common is the quality of mind that enables one to directly perceive or experience the reality to which they both point. This quality of mind is referred to as a "non-judgmental" or "choiceless" awareness. Although meditators hear about this state of mind quite frequently, it is not until they recognize that it is one of the primary causes and conditions for the arising of insight that its true significance is appreciated.

The consequence of making judgments is to perpetuate obsessive patterns of mind. If we judge the contents of mind to be good, positive, or fortunate, we grasp at them. By doing so the presence of these patterns are reinforced. If we judge the contents of mind to be important, we focus on them, watching to see where they will lead. If we judge the contents of mind to be bad, negative, or unfortunate, we tend to resist them. Although the patterns will be suppressed, they will continue to persist on an unconscious basis. Every form of reactivity to our mental patterns actually invests them with additional power to influence us.

It is not easy to cultivate a non-judgmental or choiceless awareness. However, the consequences of remaining present in this way are quite significant. Issues that have been deeply repressed begin to rise to the surface providing us with the opportunity to consciously address them. By recognizing our self-destructive patterns, their power to control our behaviors diminishes. Our attachments typically decrease as we discover more subtle levels of impermanency and realize our inability to stop or control the incessant rise and fall of phenomena. We may perceive the unfulfilling nature of sense experience and abandon the pursuit of meaningless goals. Ultimately, as the mind experiences the selfless nature of all phenomenal existence, it may turn for its security to the freedom of the unconditioned.

Choiceless awareness is a quality of mind that is free from making judgments, decisions or generating commentary as it meets with sense experiences. It is a mind that responds to each new moment without the burden of its past history or of making future projections. When the mind no longer clings anywhere, not even to the idea of not clinging anywhere, we realize, either suddenly or gradually, that we truly already are that for which we have been searching.

Also from Matthew Flickstein's excellent introductory book to the Visuddhimagga, The Meditators Atlas:

REMAINING PRESENT WITH CHOICELESS AWARENESS

From the beginning of our practice of insight meditation, we have been using the breath (or another object from one of the four foundations of mindfulness) as the primary focus of our awareness. Whenever the mind strayed from this primary object , we noticed the impermanent, unsatisfactory, and selfless nature of the new object, and then gently but firmly returned to the breath. We used the primary object as an anchor that kept our awareness centered on what was occurring during each present moment. At this stage in our spiritual development, however, this practice technique has a significant drawback.

The purpose of insight meditation is to see things as they really are. In order for this to happen, we need to be choicelessly aware of whatever arises, without grasping or resisting any of our experiences. Whenever we have an intention to move our attention in a particular direction (back to the breath, for example), we are subtly manipulating the mind by creating an intention, and we are no longer choicelessly aware of what is occurring.

Many meditators have learned to mentally note or label what they are experiencing as an aid to recognizing whatever is arising to consciousness. Although the noting may be heard as a very gentle voice in the mind, at this stage of the practice the intention to note also becomes an impediment. It prevents us from being choicelessly aware of whatever is unfolding in each present moment. However, if the mind notes what it sees without any conscious intention on our part, noting is just treated as another object to watch rise and fall.

At this point in our practice, we no longer attend to any primary object. We just remain choicelessly aware of whatever arises to consciousness. Our prior work with the four foundations of mindfulness will now bear its greatest fruit. By intentionally having investigated the various aspects of the five aggregates, our mind will be less inclined to find interest in any of the phenomena it experiences. Since we are not grasping or resisting our sensory experiences, they will appear to arise and disolve with remarkable speed. This recognition will enable us to gain deeper insights into the impermanent, unsatisfactory and selfless nature of all conditioned phenomena.

In order for us to meditate in this manner, our momentary concentration needs to be well developed. It requires that we stay present with the waves of sensory experience as they incessantly break on the shore of our consciousness. If during this practice our mind loses its balance and gets swept away with what is being experienced, we return to using the breath as an anchor until our momentary concentration has regained its stability. Once that occurs, we let go of the breath, once again remaining choiclessly present with whatever is occurring.